On Cooperation in Energy Limited Wireless Networks

This paper considers wireless networks with energy limited nodes. In this scenario, multi-hop forwarding is needed to minimize the network energy consumption. In many practical scenarios, however, nodes´ selfishness raises doubts on whether each node will be willing to forward packets in order to minimize the overall energy expenditure. To analyze this problem, a non-cooperative game theoretic approach is adopted in our work. Using this framework, the critical role of altruistic nodes in encouraging cooperation is established. More specifically, we show that it is sufficient to have a vanishingly small fraction of the nodes to be altruistic, i.e., relay nodes, in order to ensure full cooperation from all the nodes in the network. This result hinges on using the appropriate forwarding policies by the altruistic nodes, as detailed in the sequel. An important aspect of our work is that only reward/punishment policies that can be realized on the physical layer are used, and hence, our results establish the achievability of full cooperation without requiring additional incentive mechanisms at the higher layer.